The proposed project is a book-length history of electroencephalography during the 20th century. Electroencephalography is a technique of recording the electrical activity of the brain from the surface of the scalp (EEC) that was developed during the late 1920s and 1930s. EEG research rapidly transformed the understanding, diagnosis, classification and treatment of the epilepsies and had a broad impact on the fields of physiology, psychology, neurology, and neurosurgery. Relying on analysis of published scientific literature and archival materials, this project will accomplish four major objectives. The first is to provide a detailed history of the development of electroencephalography in North America, England and.Europe with emphasis on the role of technical innovations, standardized recording techniques, advanced computational methods and the cultural context of EEG research. The second goal is to use the history of electroencephalography during the mid-20th century to probe the complex interaction between clinical medicine and evolving technologies, focusing on the way in which specific clinical goals shape the design, construction, and implementation of novel techniques. The third objective of this historical project is to look beyond the discipline of electroencephalography to its broader impact on medicine and neuroscience. The EEG constituted a major paradigm for brain research during the 20th century, and I will explore the impact of EEG research on the care of patients with epilepsy, on the scientific study of sleep and consciousness, and on the development of both scientific and popular views on brain function. The fourth and most challenging aspect of this project is to develop an epistemological model of scientific progress in clinical neuroscience based on the history of electroencephalography that is applicable to contemporary developments in neuroimaging and neurogenetics. Lay Description: This project traces the history of brain wave research or electroencephalography (EEG) during the 20th century, focusing on technical developments in EEG research and their impact on the understanding and treatment of epilepsy and other neurological conditions. In addition, the broad impact of EEG research on neuroscience is explored and a model of scientific progress is developed.